Method and apparatus for introducing comminuted material into a fluid stream



M KINLEY STOCKTON I 1,986,300 METHOD AND APPARATUS FOR INTRODUCING COMMINUTED Jan. 1, 1935.

MATERIAL INTO A FLUID STREAM Filed Nov. 26, 1932 Patented Jan. 1, 1935 UNITED STATES METHOD AND APPARATUS FOR INTRO- DUCING COIVIMINUTED MATERIAL INTO A FLUID STREAM McKinley Stockton, ,Los Angeles, Calif.,

to The Dicalite Company, Los Angeles assignor Calif.,

a corporation of Delaware Application November 26, 1932, Serial No. 644,546

2 Claims.

This invention relates to the treatment and handling of finely divided diatomaceous earth, and particularly pertains to a method and apparatus for introducing the comminuted earth into a stream of air under pressure.

In the manufacture of diatomaceous earth products it has been found that the efficiency of the product is in direct proportion to the extent to which the structure of the diatoms is preserved during the milling operation. It has been ascertained that this structure may be best preserved by an operation in which the particles are milled by attrition against each other. After a suitable milling it may become necessary to mix various grades of milled products, and heretofore it has been common practice to mix the products and thereafter transmit them through a blower in suspension in an air stream.

Mixing may be required because it is customary to divide the bagged product into groups representing operating periods, usually of two hours duration. Samples of the material produced are taken during each period from every fifth bag. These samples are composited into period samples and tested according to standard methods. It frequently happens that due to'the natural variation in the crude diatomaceous earth the finished product varies widely with respect to certain desirable properties. When these variations exceed certain limits the product is set aside and it is the principal object of the present invention to provide means whereby the various products may be suitably blended without producing an over-milled condition of the product and a poor blend of the various grades introduced into a mixture. I

It is a further object of the invention to provide a process whereby various grades of material may be worked and mixed without remilling to obtain a desired grade of product and to make it possible to utilize low grade products which would otherwise be wasted. The invention contemplates meansfor pneumatically transmitting milled diatomaceous earth and the like to suitable storage and packing stations, during which time a separately milled product may be introduced into the flowing stream of moving material, and for refeeding andjurther blending of" various grades without the use of complicated apparatus.

The invention is illustrated by way of example in the accompanying drawing in which:- Figure 1 is a view in diagram showing the apparatus with which the present invention is concerned.

Fig. 2 is a view in diagram showing the appa ratus as seen on the line 22 of Fig. 1.

The apparatus generally indicated in the drawing comprises a blower 10 into which a comminuted diatomaceous earth is delivered by a central feed pipe 11. The earth is delivered by the blower to a cyclone separator 12 and in transit it may receive from a hopper 13 another earth or grade which is to be blended with the material passing from the blower and which may be fresh material or refed material, as the case may be.

The point in the system at which the material is returned and refed is of great importance. In some instances in the prior art it has been returned directly to the bins preparatory to packing. This practice has, as a rule, produced a poorlyblended product which is liable to have a wide variation in character from bag to bag, depending-upon the amount of refed material which it contains. In some instances in the prior art it has been the practice to refeed the material by delivering it directly to the suction side of the blower 10 and introducing it into the induction pipe 11. This results in an undesirable remilling or the previously milled material which produces an over-milled product having the characteristic of a reduced flow rate and an increased density, as well as other undesirable qualities.

I have discovered that by returning the refed product to the pressure side of the blower 10 rather than to the suction side a desired blending of products may be obtained, while at the same time the remilling of the product in the blower is avoided.

As shown in the introduced on the pressure side of the blower 10 by connecting a feed pipe 14 with the bottom of the hopper 11. This feed pipe also communicates with a vertical eduction pipe 15 by which communication isestablished between the blower 10 and the cyclone 12. A gate valve 16 is provided in the pipe 14 to close on the material when desired. Mounted in the pipe 14 is a combined valve and feed screw 1'7 which is carried on a shaft 18'and acts to convey material from the bottom of the hopper 13 through the pipe 14 and into the eduction pipe 15. The conveyor shaft 18 is mounted in suitable bearings 19 and is here shown as provided with a sprocket wheel 20 driven from a sprocket 21 by a chain 22.

The sprocket 21 is mounted upon a shaft 23 drawing the product may be carried in bearings 24 and supported in a vposipacking means.

with the pipe 33 and when a valve 35 is ma- 'nipulated the material from the pipe 33 is detion parallel to the shaft 18 across the hopper 13 and above the conveyor screw 1'7. This shaft carries a plurality of agitator blades 25. The shaft 23 is driven by a sprocket wheel .26 fitted with a sprocket chain 2'7 which leads around shaft 28 of a power unit 29. The power unit may be of any preferred design although it is here shown as comprising a motor 31 which drives a suitable gear set connected with' a sprocket 28. The material delivered to the cyclone 12 is classified and the heavy material drawn off through the pipes 32 at the bottom of the cyclone 12 while the lighter material passes through pipe 33 to suitable storage or A refeed pipe 34 is'connected livered to the hopper 13 for refeeding.

In operation of the present invention a desired grade of material is fed into the suction pipe 11 from any suitable source. This pipe usually communicates with a center of the housing of fan 10 where it is fed into a fan rotor 36 which comprises a plurality of radial blades adapted to engage the material and to throw it tangentially into the eduction pipe 15. This material with the air in which it is suspended will then be forced upwardly under pressure through the pipe 15 and into the cyclone separator 12. As it is forced upwardly another grade of material may be introduced into the fluid stream from the storage hopper 13. This material is fed at ,a desired rate of speed by the feed screw 17 which screw will positively feed the material from the hopper 13 into the eduction pipe 15 and will also act to seal the hopper with relation to the pipe 15 to prevent back pressure from the fan into the hopper 13. When the hopper 13 is emptythe gate 16 .may be closed.

Attention is called to the fact that milled diatomaceous earth usually ranges in size from particles of the order of 100 microns to particles of the order of one-half micron. In general the greater the proportion of the finer particles the lower will be the filtering efiiciency and the higher the wet density of the product. Such diatomaceous earth is usually conveyed by air in the milling process and it is customary to use cyclone separators, such as generally indicated at 12 in the drawing, to remove the earth from the air. Such separators collect the bulk of the ,material but allow some of thefine particles 'to escape with the air. There is thus selective air separationwhich has a tendency to raise the filtration efliciency and lower the wet density of the materialk Sub standard diatomaceous earth usually contains an excess of fine particles and is thus wreadily improved by further air separation. when such substandard diatomaceous eartli is refed to the pressure side of the blower 10 in the manner previously described it is not only blended with the milled product without detrimental remilling but it is also subject to extra air separation which improves its quality.

The'apparatus which I have here shown may be also used to improve sub standard diatomaceous earth when no other material is being handled in the mill. This is done bypassing the earth into the air stream on the pressure side of'the blower and from the hopper 13. This secures an extra air separation for the product without remilling it as would be the case if it were passed through the blower. By this operation the filtration efliciency of the product will be raised and the wet density of the product will be lowered. This will also improve the other desirable general characteristics of the product.

Special materials 'may be produced with this apparatus by refeeding standard diatomaceous earth powders through it to the pressure side of the blower 10 and thus subjecting these products to additional air separation. By making several passes of the material through the separation step powders possessing superlative filtration characteristics may be obtained.

While I have shown the preferred form of apparatus now known to me and a preferred method of operating the same, it will be understood that various changes might be made in the combination, construction, and arrangement of parts, and the steps of the method, without departing from the spirit of the invention as claimed.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. Apparatus for simultaneously comminuting diatomaceous earth and blending the comin comminuted form in suspension in said air.

stream; means for substantially separating comminutedearth from an air stream; a channel.

affording communication between theintake side of said separating means and the discharge side of said blower, and means .for introducing a stream of said previously comminuted earth into said channel on the discharge side of said blower.

2. The method of simultaneously comminuting diatomaceous earth and modifying its properties by intermixture with'another diatomaceous earth,-which comprises: suspending the earth to be comminuted in a flow stream of air; subjecting said earth in said suspension to a comminuting effect; introducing into said air stream a stream of a previously comminuted earth at a point following said comminuting effect, thereby producing suspension of last said earth in said air stream and its intermixture with first said earth without further comminution of last said earth, and finally subjecting said air stream to ,a; separating effect whereby said intermixed earthsare substantially separated from said air.

" McKINLEY STOCKTON. 

